Conventional rovers and wheeled vehicles typically consist of many hard material-based parts that constitute the chassis and rotating components (e.g., rims of wheels, axles, transmission, and motors). With the exception of the tires and suspension, general design principles base material selection on high strength and elastic modulus.
While there are many advantages to using hard materials in these applications, there have been a range of efforts to incorporate soft materials into land-based locomotors. Two of the most notable ones consist of recent efforts in the motion of tensegrity-based structures and bending/extending soft robots based on large induced strains. While tensegrity-based robots are capable of rolling, both classes of soft robots have a similar dilemma to that found in nature: the lack of wheels. It would thus be desirable to have rotary actuators based on inflatable elastomeric structures, which avoid the disadvantages of state-of-the-art soft robots, particularly with respect to the limited rotational capabilities of such soft robots.